Regarding Ewoks in ROTJ, I remember seeing something years ago, that Lucas originally wanted to make a planet of Wookies.
It could’ve been on a Discovery Channel program. However, since the Chewbacca costume was made of horse hair, and was extremely expensive, they had to change it completely. Make a planet of small creatures, using less expensive material. The name Ewok came from Economical Wookie = EWOK.Yak hair actually. And what the heck is a Wookie? 😉
Well, that sounds even more expensive than Horse hair. Oops, Wookiee.